Assist Lincoln, maybe, getting close to president (4)
I believe the answer is:
abet
'assist' is the definition.
(abetting is a kind of assisting)
'lincoln maybe getting close to president' is the wordplay.
'lincoln maybe' becomes 'abe' (Abraham 'Abe' Lincoln).
'getting' is a charade indicator (letters next to each other).
'close to' suggests the final letters (the 'close' to the word).
The last letter of 'president' is 't'.
'abe'+'t'='ABET'
(Other definitions for abet that I've seen before include "Criminally endorse" , "Aid - connive with" , "Urge on, help" , "Assist (a criminal)" , "Assist illegally" .)